The present invention relates to a disk management method used in a server that boots an operating system from an external disk.
In general, in a server system having disk devices, the operating system of the server is installed on the boot disk, one of the disk devices and, when the server is started, the boot disk is detected to boot the operating system.
One of the prior art technologies is that the system is booted from a fixed disk built in the server. According to this prior art, a disk device on which the operating system is to be installed is provided in the server in advance, and the operating system is installed on that disk for booting the server. In this case, only one boot disk is prepared for the server and, in addition, the boot disk is not shared with other servers.
Therefore, this prior art technology reduces the chance of other servers referencing or updating the boot disk, thus ensuring high security. Another boot method is that an external disk array device is used for booting. A disk array device, with a large storage capacity, can be connected to a plurality of servers via a fiber channel or a fiber channel switch. Booting an operating system from an external disk such as a disk array device has a security problem. A disk array device is basically like a network; that is, all servers connected to a disk array device can reference or update the disks in the disk array device. Therefore, there is a possibility that some other server alters the boot disk or references its contents.
To solve this problem, a disk array device uses a unique device identifier WWN (World Wide Name), an identifier owned by a fiber channel device, to implement a function that associates the WWN of a particular server with a disk in the disk array device. For example, a disk array device has an access range limiting function that allows server 1 with the name of WWN1 to access only disk 1 included in the disk array device. This function can maintain the security of the disks among servers. However, because a WWN is an identifier recorded in the fiber channel adapter in a server, the operating system must be started and a program (agent) for acquiring the WWN must be started to acquire the WWN. Therefore, because the WWN is not yet determined when the operating system is installed, the security function of the disk array device cannot be used until the operating system is installed and then the agent is started to acquire the WWN. This means that there is a period during which the security is low.
One alternative method is to investigate the WWN of a server before installing an operating system and to set up the security function of the disk array device. However, this method sometimes generates an error because a manual operation is involved and, in addition, requires time for setting up the function for many servers. On the other hand, a technology for acquiring a WWN without using an agent is disclosed in U.S. Patent Application Publication No. 2004/0059816A1 and the corresponding Japanese patent application JP-A-2004-118250. This method acquires the WWN of an accessed device of a disk array device to obtain information on the connection relation of the fiber channel. A problem with this method is that the relation between a server and a WWN is unknown and therefore the method cannot be used when an operating system is installed into a server.